Now \(\operatorname{Sp}_{2n}({\mathbb {Z}})\)  is a Chevalley group of Lie type \(C_n\) . By [1]}, [2]}, [3]} it has a natural extension,
its Steinberg group \(\operatorname{St}(C_n,{\mathbb {Z}})\) ,
which is defined by means of a presentation by generators and relations.
